My husband raised chickens. I've heard more than anyone should probably know about what they'll eat, given a chance. (Though the stories about the rooster coming up to the house and pounding on the door, demanding Cheerios from my husband's younger sister so he could show off to his harem, were the best.
)
The problem is, the meat industry apparently thinks it's ok to feed animal parts to all sorts of animals that wouldn't eat meat on their own, the most egregious examples being cows and sheep. Unlike human beings (and pigs), who are biologically omnivores, cows and sheep aren't meant to be eating anything but vegetation, let alone one another. If I hadn't become a vegetarian already, learning about CJD would have done it.
I'd recommend that you folks who are still eating meat check your sources, and go for organic, and range-fed if at all possible. Quite apart from the ethics of world hunger (which is a big part of my own vegetarianism), the health issues associated with eating meat are pretty scary.
Though I have to admit that the way vegetables get handled these days, they're sometimes not much better.
I would like to point out, however, that salmonella and e coli don't naturally grow on vegetables-- that's cross-contamination from the meat industry again.